Ambrosia, purveyors of fine Macintosh software since the dawn of time, have released a great utility called Wiretap. Those familiar with Rogue Amoeba's Audio Hijack will recognise what Wiretap does: it simply allows the user to record sound playing through their Mac, whether it be from a Realplayer stream, a DVD movie or from iTunes. What sets this utility apart from Audio Hijack is that it's free.
Wiretap does not record from an external source, so ripping audio directly from vinyl isn't possible. Neither does it encode MP3 files, such is the high cost of licencing the MP3 codec; instead, the software outputs AIFF files which can then be converted to MP3 using iTunes. These omitted features aside, Wiretap is another high quality, simple utility from Ambrosia. They make great rice pudding too.